Touch panel device and method for manufacturing touch panel devices

ABSTRACT

Each of transducers of a touch panel device includes a piezoelectric thin film, a plate electrode disposed at one surface of the piezoelectric thin film and a comb-like electrode disposed at the other surface of the piezoelectric thin film. The comb-like electrode has a plurality of comb-like electrode fingers and a linear bus electrode to which one end of each of the plural comb-like electrode fingers is connected. A plurality of wiring electrodes is provided at the outer side of any of the transducers in parallel with the bus electrode of the transducer and is connected to the bus electrode and the plate electrode of any of the transducers. Each of the wiring electrodes includes an electrode base portion formed by printing silver paste containing fine particles on the substrate and an electrode main body formed by printing silver paste containing large particles and fine particles in a mixed manner on the electrode base portion.

This application is a divisional of Application Ser. No. 11/017,860filed Dec. 22, 2004, the entire contents of which are incorporatedherein by reference, which is based upon and claims the benefit ofpriority from the prior Japanese Patent Application No. 2004-241065,filed on Aug. 20, 2004, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a touch panel device that determines atouch position of an object by detecting attenuation position of asurface acoustic wave due to a touch of the object. The touch paneldevice is used as an input device of a personal computer or a personaldigital assistant, for example.

2. Description of the Prior Art

As an input device of a personal computer, a mobile computer, a personaldigital assistant device (PDA) or the like, the touch panel device isoften used in which information can be entered with the touch of afinger or a pen on a display screen of a display device.

There are two types of the touch panel devices. One utilizes aresistance film, and another utilizes a surface acoustic wave (SAW). Theresistance film type has a multilayered resistance film in a touch area,which scatters light so that transmittance is low. A touch panel deviceof the surface acoustic wave type has transducers that are arranged atfour sides of the touch area for emitting or receiving the surfaceacoustic wave. When a finger or the like touches the touch area, thetouch position is detected in accordance with the attenuation positionof surface acoustic wave. The surface acoustic wave type has anadvantage of a high transmittance, a good visibility of the displayscreen and a high durability against a scratch because the touch areahas no resistance film or the like.

The applicant proposed a structure of the surface acoustic wave typetouch panel device in Japanese unexamined patent publication2004-171213. This structure has a single phase transducer (SPT) of anelectrode structure in which a piezoelectric thin film is sandwichedbetween a comb-like electrode and a plate electrode so that only oneelectrode is disposed on one surface. The structure also has a chevrontype electrode structure in which dog-legged comb-like electrodes arearranged in a row.

The touch panel device includes a rectangular transparent substrate andtotal four transducers. Emitting transducers are disposed at the upperend portion and the lower end portion of the substrate while receivingtransducers are disposed at the left end portion and the right endportion. The portion surrounded by the four transducers is the toucharea. Each of the transducers has the SPT electrode structure describedabove and the chevron type electrode structure.

Each of the transducers has one end in the longitudinal direction wherea wiring electrode and a connection portion between the comb-likeelectrode and the plate electrode are disposed closely to each other. Anexcitation voltage supplied via the wiring electrode is applied to theconnection portion so that signal power supply is performed. Inaddition, a received signal is obtained from the connection portion tothe wiring electrode so that signal fetch is performed. The other end ofeach of the wiring electrodes is drawn as a wire connection portion toone position of the substrate and is connected to a signal processcircuit via a flexible cable or the like that is attached to the wireconnection portion.

The excitation voltage is applied to the transducers disposed at theupper end and the lower end portions so as to generate surface acousticwaves. The generated surface acoustic wave propagates on the substratein a diagonal direction and is received by the transducer disposed atthe right or the left end portion. When a finger, a pen or the liketouches a point in the touch area, the surface acoustic wave isattenuated at the touched point. Therefore, the touched position can bedetected by a signal process in accordance with the position where alevel of the received signal is attenuated.

In the above-mentioned touch panel device, it is desirable to enlargethe touch area TE and reduce an area for transducers as much aspossible. Especially, a small type touch panel device that is used for aPDA or the like is required to have a narrow bezel in which transducersand wiring electrodes are embedded for realizing a compact size of thePDA or the like.

The above-mentioned SPT structure of transducer, in which only oneelectrode is disposed on each surface of a piezoelectric thin film, hasan advantage for reducing its width which corresponds to a width of abezel portion, to an opposed electrode structure in which two electrodesare disposed on one surface. Therefore, the former has an advantage forreducing a width of a bezel to the latter.

However, wiring electrodes for supplying power to transducers arearranged along the outer rims of the transducers, so the portion for thewiring electrodes should be made in a small width as much as possible.However, in order to reduce the width of the wiring electrode, it isnecessary to increase a height of the wiring electrode so as to maintaina cross-sectional area thereof for preventing increase of resistancethereof. It is not good to increase a thickness of the touch paneldevice for increasing a height of the wiring electrode.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a touch panel deviceand a method for manufacturing touch panel devices in which a width of abezel portion of the touch panel device can be reduced as much aspossible while preventing increase of a thickness of the touch paneldevice.

The touch panel device according to one aspect of the present inventionincludes a transparent substrate, a touch area disposed at the middleportion of the substrate and transducers disposed at the peripheralportion of the touch area for exciting or receiving surface acousticwaves. Each of the transducers includes a piezoelectric thin film, aplate electrode disposed at one surface of the piezoelectric thin filmand a comb-like electrode disposed at the other surface of thepiezoelectric thin film, the comb-like electrode consisting of aplurality of comb-like electrode fingers and a linear bus electrode towhich one end of each of the plural comb-like electrode fingers isconnected. A plurality of wiring electrodes is provided at the outerside of the transducer in parallel with the bus electrode of thetransducer and is connected to the plate electrode and the bus electrodeof any of the transducers. Each of the wiring electrodes includes anelectrode base portion formed by printing silver paste containing fineparticles on the surface of the substrate and an electrode main bodyformed by printing silver paste containing large particles and fineparticles in a mixed manner on the electrode base portion.

Preferably, the plural comb-like electrode fingers and the bus electrodeare arranged on the other surface of the piezoelectric thin film and areformed by printing silver paste containing fine particles in the sameprocess as the electrode base portion.

More preferably, a girdle wall made of zinc oxide is formed between twoof the plural wiring electrodes for preventing migration when the wiringelectrode is printed.

In another embodiment, the bus electrode includes a bus electrode baseportion formed by printing silver paste containing fine particles on thesurface of the substrate and a bus electrode main body formed byprinting silver paste containing large particles and fine particles in amixed manner on the bus electrode base portion.

In this case, it is preferable that a girdle wall made of zinc oxide beformed between two of the plural wiring electrodes as well as betweenthe wiring electrode and the bus electrode.

In addition, it is preferable that an acoustic absorption moisture prooflayer be formed over the entire area of an edge portion of the substrateso as to cover the plural wiring electrodes and the bus electrode.

The plate electrode is disposed between the piezoelectric thin film andthe substrate, a contact portion for connecting the plate electrode withthe wiring electrode is a part of the plate electrode extending from andunder the piezoelectric thin film onto the substrate, and the contactportion is covered with the acoustic absorption moisture proof layer.

A method for manufacturing a touch panel device according to the presentinvention includes the steps of forming the plate electrode on a surfaceof the substrate, forming the piezoelectric thin film on the plateelectrode, forming the plural comb-like electrode fingers and the buselectrode on the surface of the piezoelectric thin film at the same timeas forming an electrode base portion of a wiring electrode that isconnected to the plate electrode and the bus electrode on the surface ofthe substrate by printing silver paste containing fine particles, andforming an electrode main body of the wiring electrode on the electrodebase portion by printing silver paste containing large particles andfine particles in a mixed manner Another method for manufacturing atouch panel device includes the steps of forming the plate electrode ona surface of the substrate, forming the piezoelectric thin film on theplate electrode, forming the plural comb-like electrode fingers on thesurface of the piezoelectric thin film at the same time as forming anelectrode base portion of each of the bus electrode and a wiringelectrode that is connected to the plate electrode and the bus electrodeon the substrate by printing silver paste containing fine particles, andforming electrode main bodies of the bus electrode and the wiringelectrode on each of the electrode base portions by printing silverpaste containing large particles and fine particles in a mixed manner.

As necessary, the step for forming the piezoelectric thin film includesforming the piezoelectric thin film using zinc oxide and simultaneouslyforming a girdle wall using the zinc oxide between two of the pluralwiring electrodes on the substrate so as to prevent migration when thewiring electrode is printed.

According to the present invention, a width of a bezel portion of thetouch panel device can be reduced as much as possible, while increase ofa thickness of the touch panel device is prevented.

According to another aspect of the present invention, migration whenprinting the wiring electrode can be prevented, so a space between thewiring electrodes can be reduced resulting in a smaller width of thebezel portion of the touch panel device.

According to another aspect of the present invention, invasion ofmoisture into a contact portion of the plate electrode with the wiringelectrode can be prevented, so generation of corrosion due to a batteryeffect can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a touch panel device according to a firstembodiment of the present invention.

FIG. 2 is an enlarged view of a part of the touch panel device.

FIG. 3 is a cross sectional view of a portion of a transducer shown inan enlarged manner.

FIG. 4 shows a position of a connection portion.

FIG. 5 shows an example of a voltage distribution of the transducer.

FIG. 6 shows waveforms of an excitation signal and a received signal.

FIG. 7 is a diagram for explaining a general process for manufacturingthe transducer.

FIG. 8 is a cross section showing an example of providing an anchor at abase portion of the wiring electrode.

FIG. 9 is a cross section of a portion of the transducer of the touchpanel device according to a second embodiment of the present inventionshown in an enlarged manner.

FIG. 10 is a plan view corresponding to FIG. 9.

FIG. 11 is a cross sectional view of a portion of the transducer of thetouch panel device according to a third embodiment of the presentinvention shown in an enlarged manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be explained more in detail withreference to embodiments and drawings.

First Embodiment

FIG. 1 is a plan view of a touch panel device 1 according to a firstembodiment of the present invention, FIG. 2 is an enlarged view of apart of the touch panel device 1, FIG. 3 is a cross section of a portionof a transducer 20 and wiring electrodes 30 and 31 of the touch paneldevice 1 shown in an enlarged manner, FIG. 4 shows a position of aconnection portion SB, FIG. 5 shows an example of a voltage distributionof the transducer 20, FIG. 6 shows waveforms of an excitation signal anda received signal, FIG. 7 is a diagram for explaining a general processfor manufacturing the transducer 20, FIG. 8 is a cross section showingan example of providing an anchor 35 at a base portion of the wiringelectrodes 30 and 31.

As shown in FIG. 1, the touch panel device 1 includes a rectangulartransparent glass substrate 11, four transducers 20 a-20 d disposed atthe periphery of the substrate 11, and wiring electrodes 30 a-30 d and31 a-31 d disposed at the edge portion of the transducers 20 a-20 d. Atthe middle portion of the touch panel device 1, there is a touch area TEthat is a rectangular portion surrounded by the transducers 20 a-20 d.

Two transducers 20 a and 20 b disposed at the upper and the lower sideportions are used for excitation, while two transducers 20 c and 20 ddisposed at the right and the left side portions are used for reception.An excitation voltage (or an excitation signal as shown in FIG. 6) isapplied to the transducers 20 a and 20 b for excitation so as togenerate surface acoustic waves, which propagate in the diagonaldirection on the glass substrate 11 and are received by the transducers20 c and 20 d for reception.

More specifically, the surface acoustic wave generated by the transducer20 a at the upper side portion propagates diagonally in the lower rightdirection (channel 1) and in the lower left direction (channel 2), whichare received by the transducers 20 c and 20 d disposed at the right andthe left side portions, respectively. The surface acoustic wavegenerated by the transducer 20 b at the lower side portion propagatesdiagonally in the upper right direction (channel 3) and the upper leftdirection (channel 4), which are received by the transducers 20 c and 20d disposed at the right and the left side portions, respectively. Notethat the excitation voltage is applied to the transducers 20 a and 20 bfor excitation at different timings.

The time necessary for propagation of a surface acoustic wave isproportional to the propagation distance, so the arrival time of thesurface acoustic wave at the transducers 20 c and 20 d for reception isdelayed more as farther from the transducers 20 a and 20 b fortransmission. Therefore, the received signal in the transducers 20 c and20 d for reception continues from the first arrival to the last arrivalof the surface acoustic wave with a little attenuation so as to form atrapezoid signal (see FIG. 6). If a finger, a pen or the like touchesone point in the touch area TE, the surface acoustic wave is attenuatedat the touched portion. The touch position is detected in accordancewith the position where the level of the received signal is attenuated.

The transducers 20 a-20 d have the same structure. Therefore, thestructure of the transducer will be described only about one transducer20 a. In this description and in the attached drawings, a whole set ofthe transducers 20 a-20 d or a part thereof may be referred to as a“transducer 20”.

Note that the transducer 20 and the wiring electrodes are drawn in alarger scale than the touch area TE in FIG. 1. Real dimensions are asfollows, for example. A length of one side of the glass substrate 11 isa few centimeters to a few tens centimeters, a thickness of the same isa few tenth millimeters to a few millimeters, and a width of eachtransducer 20 is approximately a few millimeters. Namely, most of thesurface of the glass substrate 11 is occupied by the touch area TEexcept for the peripheral small area. In addition, a scale in thevertical direction is larger than a scale in the horizontal direction inFIG. 3.

As shown well in FIGS. 2 and 3, the transducer 20 a has a structure (theSPT structure) in which a piezoelectric thin film 21 is sandwichedbetween a plate electrode 22 and a comb-like electrode 23. The comb-likeelectrode 23 includes a plurality of comb-like electrode fingers 24, 24,24 . . . each of which has a dog-legged shape in the plan view, a linearshaped bus electrode 25 that is connected to one end of each of theplural comb-like electrode fingers 24. Note that the plate electrode 22is opposed to the comb-like electrode fingers 24 of the comb-likeelectrode 23 via the piezoelectric thin film 21.

The piezoelectric thin film 21 is made of zinc oxide (ZnO) and has athickness of approximately 2 microns for example and a width ofapproximately a little more than 2 mm for example. The plate electrode22 is made of aluminum, for example and has a thickness of approximately0.4 microns for example and a width of approximately 2 mm for example.The comb-like electrode 23 is formed by printing nano silver paste(silver paste consisting of fine particles) and baking it, for example.The comb-like electrode finger 24 has a thickness of approximately1.0-1.5 microns for example, a width of approximately 60 microns forexample and a space of approximately 90 microns for example that means apitch of approximately 150 microns for example. The bus electrode 25 hasa thickness of approximately 2.5 microns for example and a width ofapproximately 150 microns for example.

Note that the dimensions of the piezoelectric thin film 21, the plateelectrode 22 and the comb-like electrode 23 may be other values than theabove-described values. For example, the width of the piezoelectric thinfilm 21 may be selected from the range of approximately 1-3 mm. Thethickness of the plate electrode 22 may be selected from the range ofapproximately 0.3-0.4 microns, for example. The width of the plateelectrode 22 may be selected from the range of approximately 1-2 mm, forexample. The thickness of the comb-like electrode finger 24 may beselected from the range of approximately 1-2 microns, for example. Thewidth of the comb-like electrode finger 24 may be selected from therange of approximately 50-75 microns, for example. The space between thecomb-like electrode fingers 24 may be selected from the range ofapproximately 75-100 microns, for example. The thickness of the buselectrode 25 may be selected from the range of approximately 2-3microns, for example. The width of the bus electrode 25 may be selectedfrom the range of approximately 100-250 microns, for example.

The comb-like electrode 23 and the plate electrode 22 of each of thetransducers 20 a-20 d are connected to the wiring electrodes 30 a-30 dand 31 a-31 d at the connection portion SB, respectively. Each of thewiring electrodes 30 a-30 d and 31 a-31 d is led along the outer rim ofthe transducer 20 on the glass substrate 11 and is drawn out at oneportion of the glass substrate 11 located at the lower right portion inFIG. 1 as a wire connection portion KS. The wire connection portion KSis connected to a flexible cable or the like (not shown) so as to beconnected to a signal process circuit. Note that a whole or a part ofthe wiring electrodes 30 a-30 d or 31 a-31 d may be referred to as a“wiring electrode 30” or a “wiring electrode 31”, respectively.

In FIG. 3, the wiring electrodes 30 and 31 respectively includeelectrode base portions 301 and 311 formed on the glass substrate 11 byprinting the nano silver paste and electrode main bodies 302 and 312formed by printing hybrid nano silver paste (silver paste consisting ofa mixture of large particles and fine particles) on the electrode baseportion 311. The bus electrode 25 and the plate electrode 22 areconnected to the electrode base portions 301 and 311 from each of theconnection portions SB.

Each of the electrode base portions 301 and 311 has a thickness ofapproximately 2-3 microns for example and a width of approximately 200microns for example. Each of the electrode main bodies 302 and 312 has athickness of approximately 20 microns and a width of approximately 200microns. A space between the wiring electrode 30 and the wiringelectrode 31 is approximately 200 microns, and a space between thewiring electrode 30 and the bus electrode 25 (the piezoelectric thinfilm 21) is approximately 150 microns.

Note that the dimensions of the electrode base portions 301 and 311 andthe spaces between them may be other values than the above-describedvalues. For example, the widths of the electrode base portions 301 and311 as well as the widths of the electrode main bodies 302 and 312 maybe selected from a range of approximately 100-250 microns. The spacebetween the wiring electrode 30 and the wiring electrode 31 may beselected from a range of approximately a few tens microns to 250microns. The space between the wiring electrode 30 and the bus electrode25 (the piezoelectric thin film 21) may be selected from a range ofapproximately a few tens microns to 150 microns.

Silver particles of very small grain sizes at approximately a fewnanometers are used for the nano silver paste. Silver particles of verysmall grain sizes at approximately a few nanometers and silver particlesof relatively large grain sizes at approximately 1-2 microns are mixedin the hybrid nano silver paste. It is possible to remove a bindercomponent to reduce a resistivity. When using the nano silver paste, aresistivity thereof can be reduced to approximately one tenth of theconventional silver paste (in which silver particles of large grainsizes at approximately 1-2 microns are used), and a thin film having athickness of approximately 1 microns can be formed. When using thehybrid nano silver paste, a resistivity thereof can be also reduced toapproximately one tenth of the conventional silver paste. Both the nanosilver paste and the hybrid nano silver paste can be applied by multipleprinting so that a thick film can be formed. In this case, the hybridnano silver paste can form a thick film readily by printing smallernumber of times. For example, a thickness of approximately 20 micronsdescribed above can be formed by printing the hybrid nano silver pasteonce. Note that both the nano silver paste and the hybrid nano silverpaste are available on the market and are known well.

The thick film of the electrode main body 302 or 312 reduces a totalresistance of the wiring electrode 30 or 31. The electrode base portion301 or 311 prevents a migration on the glass substrate 11 in theprinting process and enables a good electrical and mechanical connectionwith the electrode main bodies 302 and 312. Consequently, the wiringelectrodes 30 and 31 having sufficiently small resistances can be formedby small cross-sectional areas.

Therefore, a width of the area for the wiring electrodes 30 and 31 canbe reduced and a height thereof can be reduced. As a result, a width ofa bezel portion of the touch panel device 1 can be reduced while athickness of the touch panel device 1 is prevented from increasing.

If the conventional silver paste is used for the entire wiringelectrodes 30 and 31, thickness thereof should be approximately 200microns that is ten times because of a high resistivity thereof. As aresult, a thickness of the transducer 20 becomes large, and the numberof times of printing will increase. Furthermore, there is a tendency ofmigration onto the glass substrate 11 during the printing process, so itis necessary to secure a sufficient space between the wiring electrodes30 and 31 and a sufficient space between the wiring electrode 30 and thebus electrode 25, resulting in a large width of the bezel portion.Furthermore, efficiency of the excited surface acoustic wave isattenuated rapidly when a film thickness of the comb-like electrode 23on the piezoelectric thin film 21 exceeds one hundredth of thewavelength (a pitch) λ of the surface acoustic wave in the transducer 20having the SPT structure, so it is difficult to increase the efficiencywhen the conventional silver paste is used and a film thickness islarge.

Note that capacitance of the comb-like electrode 23 is determinedbasically by a width and a length of the comb-like electrode finger 24and a thickness of the piezoelectric thin film 21. Therefore, it isimportant to make the comb-like electrode finger 24 in a precise width.On the other hand, a thin film is necessary for a fine pattern of thecomb-like electrode finger 24 for exciting the surface acoustic wave. Itis possible to form the comb-like electrode finger 24 and the buselectrode 25 at the same time. However, as a width of the pattern isdifferent between the comb-like electrode finger 24 and the buselectrode 25 by a few times, an optimal printing condition may bedifferent between them. To avoid this situation, a pattern in which thecomb-like electrode finger 24 and the bus electrode 25 are separatedfrom each other may be used for a good yield.

In this embodiment, the connection portion SB between the wiringelectrode 30 or 31 and the comb-like electrode 23 or the plate electrode22 is disposed at the place described below. Namely, as shown well inFIG. 4, when dividing the transducer 20 into two areas EA and EB in thelongitudinal direction M1 of the bus electrode 25, the connectionportion SB of the bus electrode 25 with the wiring electrode 30 isprovided in one area EA, and the connection portion SB of the plateelectrode 22 with the wiring electrode 31 is provided in the other areaEB.

Furthermore, in this embodiment, these two connection portions SB arelocated at the positions that divide the length of the transducer 20,i.e., the length of the area EA plus the length of the area EB intothree equally.

The transducer 20 for excitation is supplied with a power of anexcitation voltage from these two connection portions SB. Namely,connection portion SB is a power supplying point. A voltage distributionwhen the power is supplied to the transducer 20 is as follows.

In FIG. 5, the horizontal axis represents the length in the excitationarea of the transducer 20 that is approximately 120 mm at most, thevertical axis represents a voltage intensity when the power is suppliedfrom the two connection portions SB (the power supplying points 1 and2), and the curved line JR1 represents the voltage distribution.According to this graph, the voltage intensity is the minimum at thepower supplying points 1 and 2, and it increases along with distancefrom the power supplying points 1 and 2. However, there is no largevariation as a whole, and the voltage distribution is substantiallyuniform over the entire excitation area.

Note that a curved line JRj in FIG. 5 shows an example of the voltagedistribution in the case where the power is supplied from one endportion (an excitation end 1) as the conventional structure. It isunderstood from comparison between the curved line JR1 and the curvedline JRj that the curved line JR1 has a smaller variation of the voltageintensity (variation of amplitude) and a more uniform voltagedistribution than the curved line JRj.

Next, a general process for manufacturing the transducer 20 will bedescribed with reference to FIG. 7.

First, as shown in Step (a) in FIG. 7, a glass substrate 11 is prepared,and a surface thereof is cleaned. Next, a thin film 22 x of aluminum isformed on one surface of the glass substrate 11 by sputtering, vapordeposition or the like, and a resist film 61 is formed on the thin film22 x (Step (b) in FIG. 7). The thin film 22 x is etched so as to formthe plate electrode 22 (Step (c) in FIG. 7). The resist film 61 isremoved, a thin film 21 x of zinc oxide is formed, and a resist film 62is formed on the thin film 21 x (Step (d) in FIG. 7). The thin film 21 xis etched so as to form the piezoelectric thin film 21 (Step (e) in FIG.7). The resist film 62 is removed, and the comb-like electrode 23 andthe wiring electrodes 30 and 31 are formed by printing and baking (Step(f) in FIG. 7).

Furthermore, as shown by a double-dashed line in FIG. 3, an acousticabsorption and moisture proof layer 41 is formed over the entire area atthe edge portion of the glass substrate 11 so as to cover the wiringelectrodes 30 and 31, the connection portion SB and the bus electrode25. The acoustic absorption moisture proof layer 41 is formed not tooverlap the excitation area of the comb-like electrode fingers 24. Theacoustic absorption moisture proof layer 41 can be realized by forming aresin film having high acoustic absorption property on a moisture prooflayer that is formed by vapor deposition of SiO2 or the like.Alternatively, it can be realized by applying an organic insulation filmmade of a moisture proof resin that is also an acoustic absorptionmaterial. For example, an acrylic resin, an epoxy resin or the likehaving a low water permeability and a high insulating properties can beused. When using a photosensitive or an ultraviolet curing resin, it iseasy to form a film only in a desired area.

A thickness of the acoustic absorption moisture proof layer 41 isrequired to be approximately one fourth of wavelength of the surfaceacoustic wave or larger. If the acoustic absorption moisture proof layer41 is thin, the surface acoustic wave may be reflected by the end faceof the glass substrate 11, thereby a signal-to-noise ratio may bedeteriorated. For example, if the wavelength λ is 150 microns, athickness of the acoustic absorption moisture proof layer 41 is set toapproximately 40 microns, for example. The acoustic absorption moistureproof layer 41 is printed and formed to cover the entire area from anarea that does not prevent excitation to the end face of the glasssubstrate 11 so as to prevent water from entering the electrode portion.

In addition, it is desirable to structure so that a finger or the likecannot touch directly to the portion of the transducer 20. However,there is possibility that water containing acid or alkali such as ascreen cleaner or sweat may enter the touch panel device. Consideringsuch cases, a protection film is provided on the surface and the endfaces of the comb-like electrode 23 and the piezoelectric thin film 21.For example, an organic thin film is made of a material having chemicalresistance in a thin film, e.g., a fluorocarbon resin such as a cytop(registered trademark) or a benzocyclobutene (BCB) resin having anaromatic structure. Particularly, there is a BCB resin that hasphotosensitive property, which can be readily used for forming a thinfilm only in a desired area and patterned.

In this way, after forming the acoustic absorption moisture proof layer41 to cover the area of the wiring electrodes 30 and 31 and the buselectrode 25, the protection film is formed in the area including thecomb-like electrode fingers 24 and the piezoelectric thin film 21. Then,water repellent and lipophobic coating is processed on the surface ofthe touch area TE of the glass substrate 11. Thus, reliability of thetouch panel device 1 is improved.

In the embodiment described above, in order to decrease the spacebetween the wiring electrodes 30 and 31 as well as the space between thewiring electrode 31 and the bus electrode 25, a girdle (a wall) can beprovided that has an insulating property for separating them. Such agirdle is made of zinc oxide for example, and it is preferable to formthe girdle when forming the piezoelectric thin film 21, simultaneouslyby patterning.

In addition, for stronger mechanical bonding of the wiring electrodes 30and 31 with the glass substrate 11, it is preferable to provide aplurality of anchors 35, 35, 35 . . . made of a material having a goodadhesiveness on the surface of the glass substrate 11 as shown in FIG.8. As the anchors 35 form many grooves, the electrode base portions 301,311 fit in the grooves so that mechanical cohesive strength with theglass substrate 11 is increased. In this case, the anchor 35 also worksas the girdle for separating the wiring electrode 30 from the wiringelectrode 31. The anchor 35 is made of zinc oxide for example, and it ispreferable to form the anchor 35 when forming the piezoelectric thinfilm 21, simultaneously by patterning.

Thus, by providing the girdle or the anchor 35, the space between thewiring electrodes 30 and 31 as well as the space between the wiringelectrode 31 and the bus electrode 25 can be reduced so that a width ofthe bezel portion of the touch panel device 1 can be reduced more.

Second Embodiment

Here, only differences between the first and the second embodiments willbe described.

FIG. 9 is a cross section of a portion of transducer 20B and wiringelectrodes 30B and 31B of the touch panel device 1B according to asecond embodiment of the present invention shown in an enlarged manner,and FIG. 10 is a plan view corresponding to FIG. 9.

As shown in FIGS. 9 and 10, the bus electrode 25B is formed not on thesurface of the piezoelectric thin film 21B but on the surface of theglass substrate 11. Namely, the bus electrode 25B includes an electrodebase portion 251 that is formed on the surface of the glass substrate 11by printing nano silver paste and an electrode main body 252 that isformed on the electrode base portion 251 by printing hybrid nano silverpaste. The electrode base portion 251 has a thickness of approximately2-3 microns for example and a width of approximately 100-150 microns forexample. The electrode main body 252 has a thickness of approximately 20microns for example and a width of approximately 100-150 microns forexample. Thus, a resistance of the bus electrode 25B can be sufficientlyreduced while a thickness thereof can be sufficiently reduced.

Structures and dimensions of the wiring electrodes 30B and 31B aresubstantially the same as the wiring electrodes 30 and 31 of the firstembodiment. A space between the wiring electrode 30B and the wiringelectrode 31B is approximately 30-200 microns, and a space between thewiring electrode 31B and the bus electrode 25B is approximately 30-150microns. Girdles 36 and 36 are provided between the wiring electrodes30B and 31B as well as between the wiring electrode 31B and the buselectrode 25B. The girdle 36 is made of zinc oxide at the same time asformation of the piezoelectric thin film 21B. Note that the comb-likeelectrode finger 24B is formed so as to extend from the surface of thepiezoelectric thin film 21B to the bus electrode 25B by printing thenano silver paste. The acoustic absorption moisture proof layer 41B isformed over the entire area of the edge portion of the glass substrate11 so as to cover the wiring electrodes 30B and 31B and the buselectrode 25B.

The girdle 36 prevents a migration of the wiring electrodes 30B and 31Band the bus electrode 25B when they are printed, so that spaces amongthem can be reduced. Instead of the girdle 36, an anchor 35 may be usedas shown in FIG. 8. In addition, the girdle 36 may be omitted.

A width of the bezel portion can be reduced also in the touch paneldevice 1B of the second embodiment.

Third Embodiment

Here, only differences between the first and the third embodiments willbe described.

FIG. 11 is a cross section of a portion of the transducer 20C and wiringelectrodes 30C and 31C of the touch panel device 1C according to thethird embodiment of the present invention. FIG. 11 shows a cross sectioncut by a plane including a connection portion SB of a plate electrode22C with a wiring electrode 31C.

As shown in FIG. 11, the plate electrode 22C, a piezoelectric thin film21C and a comb-like electrode 23C are formed on the surface of the glasssubstrate 11. The plate electrode 22C is a thin film of aluminum havinga thickness of approximately 0.3 microns for example and is provided soas to extend a little from and under the piezoelectric thin film 21C.The piezoelectric thin film 21C is a thin film of zinc oxide having athickness of approximately 2 microns, for example. The comb-likeelectrode finger 24C is a thin film made of nano silver paste having athickness of approximately 1-1.5 microns, for example.

The plate electrode 22C is connected to the wiring electrode 31C at theconnection portion SB. Here, the connection portion SB is only a part ofthe plate electrode 22C extending from and under the piezoelectric thinfilm 21C. A contact portion of the plate electrode 22C made of aluminumwith the wiring electrode 31C made of silver can generate a potentialdifference due to a battery effect when moisture invades, and current bythe potential difference may cause corrosion. Therefore, to preventmoisture from invading the contact portion, an acoustic absorptionmoisture proof layer 41C made of a member that interrupts moisture isformed on the contact portion. Namely, the acoustic absorption moistureproof layer 41C covers the contact portion of the plate electrode 22Cwith the wiring electrode 31C. Thus, invasion of moisture into thecontact portion of the plate electrode 22C with the silver wiringelectrode 31C is prevented, so that generation of corrosion due to thebattery effect can be avoided. A material of the acoustic absorptionmoisture proof layer 41C and a method of forming the same are the sameas the acoustic absorption moisture proof layer 41 described above.

The wiring electrode 31C is led on the glass substrate 11, and the endportion thereof that is a wire connection portion KS is connected to aflexible cable (a flexible pad) 52 having an electrode 51 made of acopper alloy via an adhesive (ACF) 50 containing fine particles of gold.

In this way, the third embodiment provides a structure in which theplate electrode 22C includes a part that extends from and under thepiezoelectric thin film 21C, which is connected to the wiring electrode31C. Therefore, the portion that can generates corrosion is limited, aportion to be moisture proof or waterproof is a vary narrow area, andthe acoustic absorption moisture proof layer 41C can providesubstantially complete moisture proof effect.

It is possible to extend the plate electrode 22C that is a groundelectrode to the wire connection portion KS as it is, and to form thewiring electrode 31C on the extended plate electrode 22C. In this case,however, the contact portion of aluminum with silver becomes long, sothat the moisture proof effect by the acoustic absorption moisture prooflayer is lowered and it is difficult to prevent corrosion for a longperiod.

Note that a middle portion of the wiring electrode 31C in thelongitudinal direction is omitted in FIG. 11. In addition, though notshown in FIG. 11, the connection portion SB of the bus electrode withthe wiring electrode and the wire connection portion KS at the endportion of the wiring electrode have the same structure as the case ofthe wiring electrode 31C described above, resulting in the same effect.

In addition, a protection film 42 is provided over the entire area ofsurfaces and end faces of the piezoelectric thin film 21C, the comb-likeelectrode finger 24C and the acoustic absorption moisture proof layer41C. The protection film 42 is made of a BCB resin or the like asdescribed above. The protection film 42 has a thickness of approximately1 micron, for example. The surface of the touch area TE is covered witha water repellent and lipophobic coat. Thus, the touch panel device 1Chaving high reliability can be obtained.

In each of the embodiments described above, an electrical length fromthe connection portion SB to the wire connection portion KS in each ofthe transducers 20 a-20 d is not considered specially. However, it ispossible to make the electrical lengths to be equal to each other byarranging the wiring electrodes 30 a-30 d and 31 a-30 d and the wireconnection portion KS.

In each of the embodiments described above, the structures, the shapes,the quantities, the materials and the method of formation or the like ofthe entire or a part of the transducer 20, the wiring electrodes 30 and31 and the touch panel devices 1, 1B and 1C can be modified if necessaryin accordance with the spirit of the present invention.

The present invention can be used as an input device for a personalcomputer, mobile computer, a PDA or the like.

While the presently preferred embodiments of the present invention havebeen shown and described, it will be understood that the presentinvention is not limited thereto, and that various changes andmodifications may be made by those skilled in the art without departingfrom the scope of the invention as set forth in the appended claims.

1. A method for manufacturing a touch panel device including atransparent substrate, a touch area disposed at the middle portion ofthe substrate and transducers disposed at the peripheral portion of thetouch area, each of the transducers consisting of a piezoelectric thinfilm, a plate electrode disposed at one surface of the piezoelectricthin film and a comb-like electrode disposed at the other surface of thepiezoelectric thin film, the comb-like electrode having a plurality ofcomb-like electrode fingers and a linear bus electrode to which one endof each of the plural comb-like electrode fingers is connected, themethod comprising the steps of: forming the plate electrode on a surfaceof the substrate; forming the piezoelectric thin film on the plateelectrode; forming the plural comb-like electrode fingers and the buselectrode on the surface of the piezoelectric thin film at the same timeas forming an electrode base portion of a wiring electrode that isconnected to the plate electrode and the bus electrode on the surface ofthe substrate by printing silver paste containing fine particles; andforming an electrode main body of the wiring electrode on the electrodebase portion by printing silver paste containing large particles andfine particles in a mixed manner.
 2. The method according to claim 1,wherein the step for forming the piezoelectric thin film includesforming the piezoelectric thin film using zinc oxide and simultaneouslyforming a girdle wall using the zinc oxide between two of the pluralwiring electrodes on the substrate so as to prevent migration when thewiring electrode is printed.
 3. A method for manufacturing a touch paneldevice including a transparent substrate, a touch area disposed at themiddle portion of the substrate and transducers disposed at theperipheral portion of the touch area, each of the transducers consistingof a piezoelectric thin film, a plate electrode disposed at one surfaceof the piezoelectric thin film and a comb-like electrode disposed at theother surface of the piezoelectric thin film, the comb-like electrodehaving a plurality of comb-like electrode fingers and a linear buselectrode to which one end of each of the plural comb-like electrodefingers is connected, the method comprising the steps of: forming theplate electrode on a surface of the substrate; forming the piezoelectricthin film on the plate electrode; forming the plural comb-like electrodefingers on the surface of the piezoelectric thin film at the same timeas forming an electrode base portion of each of the bus electrode and awiring electrode that is connected to the plate electrode and the buselectrode on the substrate by printing silver paste containing fineparticles; and forming electrode main bodies of the bus electrode andthe wiring electrode on each of the electrode base portions by printingsilver paste containing large particles and fine particles in a mixedmanner.
 4. The method according to claim 3, wherein the step for formingthe piezoelectric thin film includes forming the piezoelectric thin filmusing zinc oxide and simultaneously forming a girdle wall using the zincoxide between two of the plural wiring electrodes on the substrate so asto prevent migration when the wiring electrode is printed.